Taking lens device

ABSTRACT

A optical device has a zoom lens system that is comprised of a plurality of lens units and that achieves zooming by varying unit-to-unit distances and an image sensor that converts an optical image formed by the zoom lens system into an electrical signal. The zoom lens system is comprised of, from the object side, a first lens unit having a negative optical power, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a fourth lens unit having a positive optical power. The zoom lens system achieves zooming by varying the distances between the first to fourth lens units.

[0001] This application is based on Japanese Patent Applications Nos. 2000-95247 and 2000-368343, filed on Mar. 29, 2000 and Dec. 4, 2000, respectively, the contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an optical device, or a taking lens device. More specifically, the present invention relates to a taking lens device that optically takes in an image of a subject through an optical system and that then outputs the image as an electrical signal, for example, a taking lens device that is used as a main component of a digital still camera, a digital video camera, or a camera that is incorporated in or externally fitted to a device such as a digital video unit, a personal computer, a mobile computer, a portable telephone, or a personal digital assistant (PDA). The present invention relates particularly to a taking lens device which is provided with a compact, high-zoom-ratio zoom lens system.

[0004] 2. Description of Prior Art

[0005] In recent years, as personal computers and other data processing devices have become more and more popular, digital still cameras, digital video cameras, and the like (hereinafter collectively referred to as digital cameras) have been coming into increasingly wide use. Personal users are using these digital cameras as handy devices that permit easy acquisition of image data to be fed to digital devices. As image data input devices, digital cameras are expected to continue gaining popularity.

[0006] In general, the image quality of a digital camera depends on the number of pixels in the solid-state image sensor, such as a CCD (charge-coupled device), which is incorporated therein. Nowadays, many digital cameras which are designed for general consumers, boast of high resolution of over a million pixels, and are thus approaching silver-halide film cameras in image quality. On the other hand, even in digital cameras designed for general consumers, zoom capability (especially optical zoom capability with minimal image degradation) is desired, and therefore, in recent years, there has been an increasing demand for zoom lenses for digital cameras that offer both a high zoom ratio and high image quality.

[0007] However, conventional zoom lenses for digital cameras that offer high image quality of over a million pixels are usually built as relatively large lens systems. One way to avoid this inconvenience is to use, as zoom lenses for digital cameras, zoom lenses which were originally designed for lens-shutter cameras in which remarkable miniaturization and zoom ratio enhancement have been achieved in recent years. However, if a zoom lens designed for a lens-shutter camera is used unchanged in a digital camera, it is not possible to make good use of the light-condensing ability of the microlenses disposed on the front surface of the solid-state image sensor. This causes severe unevenness in brightness between a central portion and a peripheral portion of the captured image. The reason is that in a lens-shutter camera, the exit pupil of the taking lens system is located near the image plane, and therefore off-axial rays exiting from the taking lens system strike the image plane from oblique directions. This can be avoided by locating the exit pupil away from the image plane, but not without making the taking lens system larger.

SUMMARY OF THE INVENTION

[0008] An object of the present invention is to provide an optical, or a taking lens device, which is provided with a novel zoom lens system that, despite being compact, offers both a high zoom ratio and high image quality.

[0009] To achieve this object, according to one aspect of the present invention, an optical, or taking lens device is provided with: a zoom lens system that is comprised of a plurality of lens units which achieves zooming by varying the unit-to-unit distances; and an image sensor that converts an optical image formed by the zoom lens system into an electrical signal. The zoom lens system comprises at least, from the object side thereof to an image side thereof, a first lens unit having a negative optical power, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a fourth lens unit having a positive optical power. The zoom lens system achieves zooming by varying the distances between the first to fourth lens units.

[0010] According to another aspect of the present invention, an optical, or taking lens device is provided with: a zoom lens system that is comprised of a plurality of lens units which achieves zooming by varying the unit-to-unit distances; and an image sensor that converts an optical image formed by the zoom lens system into an electrical signal. The zoom lens system is comprised of, at least from the object side, a first lens unit having a negative optical power, a second lens unit having a negative optical power, and a third lens unit having a positive optical power. The first lens unit is composed of a single lens element.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] This and other objects and features of the present invention will become clear from the following description, taken in conjunction with the preferred embodiments with reference to the accompanying drawings in which:

[0012]FIG. 1 is a lens arrangement diagram of a first embodiment (Example 1) of the invention;

[0013]FIG. 2 is a lens arrangement diagram of a second embodiment (Example 2) of the invention;

[0014]FIG. 3 is a lens arrangement diagram of a third embodiment (Example 3) of the invention;

[0015]FIG. 4 is a lens arrangement diagram of a fourth embodiment (Example 4) of the invention,

[0016]FIG. 5 is a lens arrangement diagram of a fifth embodiment (Example 5) of the invention;

[0017]FIG. 6 is a lens arrangement diagram of a sixth embodiment (Example 6) of the invention;

[0018]FIG. 7 is a lens arrangement diagram of a seventh embodiment (Example 7) of the invention;

[0019]FIG. 8 is a lens arrangement diagram of an eighth embodiment (Example 8) of the invention;

[0020]FIG. 9 is a lens arrangement diagram of a ninth embodiment (Example 9) of the invention;

[0021]FIGS. 10A to 10I are aberration diagrams of Example 1;

[0022]FIGS. 11A to 11I are aberration diagrams of Example 2;

[0023]FIGS. 12A to 12I are aberration diagrams of Example 3;

[0024]FIGS. 13A to 13I are aberration diagrams of Example 4;

[0025]FIGS. 14A to 14I are aberration diagrams of Example 5;

[0026]FIGS. 15A to 15I are aberration diagrams of Example 6;

[0027]FIGS. 16A to 16I are aberration diagrams of Example 7;

[0028]FIGS. 17A to 17I are aberration diagrams of Example 8;

[0029]FIGS. 18A to 18I are aberration diagrams of Example 9;

[0030]FIG. 19 is a diagram schematically illustrating the outline of the optical construction of a taking lens device embodying the invention; and

[0031]FIG. 20 is a diagram schematically illustrating the outline of a construction of an embodiment of the invention that could be used in a digital camera.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Hereinafter, optical or taking lens devices embodying the present invention will be described with reference to the drawings and the optical or taking lens device will be referred to as a taking lens device. A taking lens device optically takes in an image of a subject through an optical system and then outputs the image as an electrical signal. A taking lens device is used as a main component of a camera which is employed to shoot a still or a moving picture of a subject, for example, a digital still camera, a digital video camera, or a camera that is incorporated in or externally fitted to a device such as a digital video unit, a personal computer, a mobile computer, a portable telephone, or a personal digital assistant (PDA). A digital camera also includes a memory to store the image from the image sensor. The memory may be removable, for example, a disk, or the memory may be permanently fixed in the camera. FIG. 19 shows a taking lens device is composed of, from the object (subject) side, a taking lens system TL that forms an optical image of a subject, a plane-parallel plate PL that functions as an optical low-pass filter or the like, and an image sensor SR that converts the optical image formed by the taking lens system TL into an electrical signal. FIG. 20 shows a zoom lens system ZL, an optical low-pass filter PL, an image sensor SR, a processing circuits PC that would include any electronics needed to process the image, and a memory EM that could be used in a digital camera.

[0033] In all the embodiments described hereinafter, the taking lens system TL is built as a zoom lens system composed of a plurality of lens units wherein zooming is achieved by moving two or more lens units along the optical axis AX in such a way that their unit-to-unit distances vary. The image sensor SR is realized, for example, with a solid-state image sensor such as a CCD or CMOS (complementary metal-oxide semiconductor) sensor having a plurality of pixels and, by this image sensor SR, the optical image formed by the zoom lens system is converted into an electrical signal. The optical image formed by the zoom lens system has its spatial frequency characteristics adjusted by being passed through the low-pass filter PL that has predetermined cut-off frequency characteristics that are determined by the pixel pitch of the image sensor SR. This helps minimize so-called aliasing noise that appears when the optical image is converted into an electrical signal. The signal produced by the image sensor SR is subjected, as required, to predetermined digital image processing, image compression, and other processing, and is then recorded as a digital image signal in a memory (such as a semiconductor memory or an optical disk) or, if required, transmitted to another device by way of a cable or after being converted into an infrared signal.

[0034] FIGS. 1 to 9 are lens arrangement diagrams of the zoom lens system used in a first to a ninth embodiment, respectively, of the present invention, each showing the lens arrangement at the wide-angle end W in an optical sectional view. In each lens arrangement diagram, an arrow mj (where j=1, 2, . . .) schematically indicates the movement of the j-th lens unit Grj (where j=1, 2, . . .) and others during zooming from the wide-angle end W to the telephoto end T. Moreover, in each lens arrangement diagram, ri (where i=1, 2, 3, . .) indicates the i-th surface from the object side, and a surface ri marked with an asterisk (*) is an aspherical surface. Di (where i=1, 2, 3, . . .) indicates the i-th axial distance from the object side, though only those which vary with zooming, called variable distances, are shown here.

[0035] In all the embodiments, the zoom lens system is composed of at least, from the object side, a first lens unit Gr1 having a negative optical power, a second lens unit Gr2 having a negative optical power, and a third lens unit Gr3 having a positive optical power, and achieves zooming by varying the distances between these lens units. In addition, designed for a camera (for example, a digital camera) provided with a solid-state image sensor (for example, a CCD), the zoom lens system also has a glass plane-parallel plate PL, which functions as an optical low-pass filter, disposed on the image-plane side thereof. In all of the embodiments, the first lens unit Gr1 and the glass plane-parallel plate PL are kept stationary during zooming, and the third lens unit Gr3 includes an aperture stop ST at the object-side end thereof.

[0036] In the first to the eighth embodiments, the zoom lens system is built as a four-unit zoom lens of a negative-negative-positive-positive configuration. In the ninth embodiment, the zoom lens system is built as a three-unit zoom lens of a negative-negative-positive configuration. In the first to the fifth embodiments, during zooming from the wide-angle end W to the telephoto end T, the second lens unit Gr2 first moves toward the image side and then makes a U-turn to go on to move toward the object side, the third lens unit Gr3 moves toward the object side, and the fourth lens unit Gr4 moves toward the image side. In the sixth to the eighth embodiments, during zooming from the wide-angle end W to the telephoto end T, the second lens unit Gr2 first moves toward the image side and then makes a U-turn to go on to move toward the object side, and the third lens unit Gr3 moves toward the object side, but the fourth lens unit Gr4, i.e. the last lens unit, remains stationary together with the glass plane-parallel plate PL. In the ninth embodiment, during zooming from the wide-angle end W to the telephoto end T, the second lens unit Gr2 first moves toward the image side and then makes a U-turn to go on to move toward the object side, and the third lens unit Gr3 moves toward the object side.

[0037] In all of the embodiments, the first and second lens units Gr1, Gr2 are given negative optical powers. This makes it easy to build a retrofocus-type arrangement. In a digital camera, the taking lens system TL needs to be telecentric toward the image side and, by building a retrofocus-type arrangement with the negatively-powered first and second lens units Gr1, Gr2, it is possible to make the entire optical system telecentric easily. Moreover, by distributing the negative optical power needed in a retrofocus-type arrangement between the two lens units Gr1, Gr2, it is possible to keep the first lens unit Gr1 stationary during zooming. Keeping the first lens unit Gr1 stationary is advantageous in terms of lens barrel design, so that it is possible to simplify the lens barrel construction and thereby reduce the cost of the zoom lens system.

[0038] In the first, the second, and the sixth to the ninth embodiments, the first lens unit Gr1 is composed of a single lens element. By composing the first lens unit Gr1 as a single lens element, it is possible to reduce the cost of the zoom lens system by reducing the number of its constituent lens element. Moreover, composing the first lens unit Gr1 out of a single lens element helps increase flexibility in the design of lens barrels so that it is possible to simplify the lens barrel construction and thereby reduce the cost of the zoom lens system. On the other hand, in the third to the fifth embodiments, the first lens unit Gr1 is composed of two lens elements. This makes correction of relative decentered aberration possible and is thus advantageous in terms of optical performance.

[0039] In all of the embodiments, it is preferable that the zoom lens system, starting with either a negative-negative-positive or a negative-negative-positive-positive configuration, fulfill the conditions described one by one below. Needless to say, those conditions may be fulfilled singly to achieve the effects and advantages associated with the respective conditions fulfilled, but fulfilling as many of them as possible is further preferable in terms of optical performance, miniaturization, and other aspects.

[0040] It is preferable that conditional formula (1) below be fulfilled.

0.5<f1/f2<5   (1)

[0041] wherein

[0042] f1 represents the focal length of the first lens unit Gr1; and

[0043] f2 represents the focal length of the second lens unit Gr2.

[0044] Conditional formula (1) defines the preferable ratio of the focal length of the first lens unit Gr1 to that of the second lens unit Gr2. If the lower limit of conditional formula (1) were to be transgressed, the focal length of the first lens unit Gr1 would be too short. This would cause such a large distortion (especially a negative distortion on the wide-angle side) that it would be impossible to secure satisfactory optical performance. By contrast, if the upper limit of conditional formula (1) would be transgressed, the focal length of the first lens unit Gr1 would be too long. This would make the negative optical power of the first lens unit Gr1 so weak that the first lens unit Gr1 would need to be made larger in diameter, which is undesirable in terms of miniaturization.

[0045] It is preferable that conditional formula (2) below be fulfilled.

1.5<|f12/fw|<4   (2)

[0046] where

[0047] f12 represents the composite focal length of the first and second lens units Gr1, Gr2 at the wide-angle end W; and

[0048] fw represents the focal length of the entire optical system at the wide-angle end W.

[0049] Conditional formula (2) defines the preferable condition to be fulfilled by the composite focal length of the first and second lens units Gr1, Gr2 at the wide-angle end W. If the upper limit of conditional formula (2) were to be transgressed, the composite focal length of the first and second lens units Gr1, Gr2 would be too long, and thus the total length of the entire optical system would be too long. Moreover, the composite negative power of the first and second lens units Gr1, Gr2 would be so weak that these lens units would need to be made larger in external diameter. Thus, it would be impossible to make the zoom lens system compact. By contrast, if the lower limit of conditional formula (2) were to be transgressed, the composite focal length of the first and second lens units Gr1, Gr2 would be too short. This would cause such a large negative distortion in the first and second lens units Gr1, Gr2 at the wide-angle end W that it would be difficult to correct the distortion.

[0050] It is preferable that conditional formula (3) below be fulfilled, and it is further preferably fulfilled together with conditional formula (2) noted previously.

0.058<(tan ωw)²×fw/TLw<0.9   (3)

[0051] where

[0052] tan ωw represents the half view angle at the wide-angle end W;

[0053] fw represents the focal length of the entire optical system at the wide-angle end W; and

[0054] TLw represents the total length (i.e. the distance from the first vertex to the image plane) at the wide-angle end W.

[0055] Conditional formula (3) defines the preferable relation between the view angle and the total length at the wide-angle end W. If the upper limit of conditional formula (3) were to be transgressed, the optical power of the individual lens units would be too strong, and thus it would be difficult to correct the aberration that occurs therein. By contrast, if the lower limit of conditional formula (3) were to be transgressed, the total length would be too long, which is undesirable in terms of miniaturization.

[0056] It is preferable that conditional formula (4) below be fulfilled, and it is further preferably fulfilled together with conditional formula (2) noted previously.

10<TLw×Fnt/(fw×tan ωw)<50   (4)

[0057] where

[0058] TLw represents the total length (i.e., the distance from the first vertex to the image plane) at the wide-angle end W;

[0059] Fnt represents the f-number (FNO) at the telephoto end T;

[0060] fw represents the focal length of the entire optical system at the wide-angle end W; and

[0061] tan ωw represents the half view angle at the wide-angle end W.

[0062] Conditional formula (4) defines the preferable relation between the total length at the wide-angle end W and the f-number at the telephoto end T. If the upper limit of conditional formula (4) were to be transgressed, the total length at the wide-angle end W would be too long, which is undesirable in terms of miniaturization. By contrast, if the lower limit of conditional formula (4) were to be transgressed, the f-number at the telephoto end T would be too low, and thus it would be difficult to correct the spherical aberration that would occur in the third lens unit Gr3 in that zoom position.

[0063] It is preferable that the third lens unit Gr3 be composed, as in the first to the fifth and the ninth embodiments, of at least two positive lens elements and one negative lens element. Moreover, it is further preferable that, as in all of the embodiments, the third lens unit Gr3 have an aspherical surface at the image-side end thereof. Let the maximum effective optical path radius of an aspherical surface be Ymax, and let the height in a direction perpendicular to the optical axis be Y. Then, it is preferable that the aspherical surface disposed at the image-side end of the third lens unit Gr3 fulfill conditional formula (5) below at Y=0.7Ymax, and further preferably for any height Y in the range 0.1Ymax≦Y≦0.7Ymax.

−0.6(|X|−|X0|)/[C0·(N′−N)·f3]<0   (5)

[0064] where

[0065] X represents the surface shape (mm) of the aspherical surface (i.e. the displacement along the optical axis at the height Y in a direction perpendicular to the optical axis of the aspherical surface);

[0066] X0 represents the surface shape (mm) of the reference spherical surface of the aspherical surface (i.e. the displacement along the optical axis at the height Y in a direction perpendicular to the optical axis of the reference spherical surface);

[0067] C0 represents the curvature (mm⁻¹) of the reference spherical surface of the aspherical surface;

[0068] N represents the refractive index for the d-line of the object-side medium of the aspherical surface;

[0069] N′ represents the refractive index for the d-line of the image-side medium of the aspherical surface; and

[0070] f3 represents the focal length (mm) of the third lens unit Gr3.

[0071] Here, the surface shape X of the aspherical surface, and the surface shape X0 of its reference spherical surface are respectively given by formulae (AS) and (RE) below.

X=(C0·Y ²)/(1+{square root}{square root over (1−ε·C 0² ·Y ²)})+Σ( Ai·Y ¹)   (AS)

X0=(C0·Y ²)/(1+{square root}{square root over (1−C 0² ·Y ²)}  (RE)

[0072] where

[0073] C0 represents the curvature (mm⁻¹) of the reference spherical surface of the aspherical surface;

[0074] Y represents the height in a direction perpendicular to the optical axis;

[0075] ε represents the quadric surface parameter; and

[0076] Ai represents the aspherical surface coefficient of order i.

[0077] Conditional formula (5) dictates that the aspherical surface be so shaped as to weaken the positive power within the third lens unit Gr3, and thus defines the preferable condition to be fulfilled to ensure proper correction of spherical aberration from the middle-focal-length region M to the telephoto end T. If the upper limit of conditional formula (5) were to be transgressed, spherical aberration would incline too much toward the under side. By contrast, if the lower limit of conditional formula (5) were to be transgressed, spherical aberration would incline too much toward the over side.

[0078] It is preferable that, as in all of the embodiments, the zoom unit disposed closest to the image plane have a positive power, and it is preferable that the zoom unit having this positive power be composed of at least one positive lens element. In cases, as in the first, the fourth, and the sixth to the eighth embodiments, where this zoom unit having the above-mentioned positive power is composed of a single positive lens element, it is preferable that this positive lens element fulfill conditional formula (6) below.

0.05<(CR1−CR2)/(CR1+CR2)<5   (6)

[0079] where

[0080] CR1 represents the radius of curvature of the object-side surface; and

[0081] CR2 represents the radius of curvature of the image-side surface.

[0082] Conditional formula (6) defines the preferable shape of the positive lens element included in the zoom unit disposed closest to the image plane. If the upper limit of conditional formula (6) were to be transgressed, the surface of this positive lens element facing the object would be highly concave, and therefore, to avoid interference with the lens unit disposed on the object side of that surface, it would be necessary to secure a wide gap in between. This is undesirable in terms of miniaturization. By contrast, if the lower limit of conditional formula (6) were to be transgressed, the positive optical power of the object-side surface of the positive lens element would be so strong that it would be difficult to correct the aberration that would be caused by that surface.

[0083] It is preferable that the first to third lens units Gr1 to Gr3 fulfill conditional formula (7) below.

0.4<|f12/f3|<1.5   (7)

[0084] where

[0085] f12 represents the composite focal length of the first and second lens units Gr1, Gr2, at the wide-angle end W; and

[0086] f3 represents the focal length (mm) of the third lens unit Gr3.

[0087] Conditional formula (7) defines the preferable ratio of the composite focal length of the first and second lens units Gr1, Gr2 to the focal length of the third lens unit Gr3. If the upper limit of conditional formula (7) were to be transgressed, the composite focal length of the first and second lens units Gr1, Gr2 would be relatively too long. Thus, if the upper limit of conditional formula (7) were to be transgressed, the exit pupil would be located closer to the image plane, and this is not desirable. As described earlier, in a digital still camera or the like, the use of a CCD and other factors require that rays striking the image plane be telecentric, and therefore it is preferable that the exit pupil be located closer to the object. By contrast, if the lower limit of conditional formula (7) were to be transgressed, the composite focal length of the first and second lens units Gr1, Gr2 would be relatively too short. Thus, if the lower limit of conditional formula (7) were to be transgressed, it would be difficult to correct the negative distortion that would occur in the first and second lens units Gr1, Gr2.

[0088] In all of the illustrated embodiments, all of the lens units are composed solely of refractive lenses that deflect light incident thereon by refraction (i.e. lenses of the type that deflect light at the interface between two media having different refractive indices). However, any of these lens units may include, for example, a diffractive lens that deflects light incident thereon by diffraction, a refractive-diffractive hybrid lens that deflects light incident thereon by the combined effects of refraction and diffraction, a gradient-index lens that deflects light incident thereon with varying refractive indices distributed in a medium, or a lens of any other type.

[0089] In any of the embodiments, a surface having no optical power (for example, a reflective, refractive, or diffractive surface) may be disposed in the optical path so that the optical path is bent before, after, or in the midst of the zoom lens system. Where to bend the optical path may be determined to suit particular needs. By bending the optical path appropriately, it is possible to make a camera apparently slimmer. It is even possible to build an arrangement in which zooming or the collapsing movement of a lens barrel does not cause any change in the thickness of a camera. For example, by disposing a mirror after the first lens unit Gr1, which is kept stationary during zooming, so that the optical path is bent by 90° by the reflecting surface of the mirror, it is possible to keep the front-to-rear length of the zoom lens system constant and thereby make a camera slimmer.

[0090] In all of the embodiments, an optical low-pass filter having the shape of a plane-parallel plate PL is disposed between the last surface of the zoom lens system and the image sensor SR. However, as this low-pass filter, it is also possible to use a birefringence-type low-pass filter made of quartz or the like having its crystal axis aligned with a predetermined direction, a phase-type low-pass filter that achieves the required optical cut-off frequency characteristics by exploiting diffraction, or a low-pass filter of any other type.

PRACTICAL EXAMPLES

[0091] Hereinafter, practical examples of the construction of the zoom lens system used in taking lens devices embodying the present invention will be presented in more detail with reference to their construction data, aberration diagrams, and other data. Examples 1 to 9 presented below correspond respectively to the first to ninth embodiments described hereinbefore, and the lens arrangement diagrams (FIGS. 1 to 9) showing the lens arrangement of the first to the ninth embodiments apply also to Examples 1 to 9, respectively.

[0092] Tables 1 to 9 list the construction data of Examples 1 to 9, respectively. In the construction data of each example, ri (i=1, 2, 3, . . .) represents the radius of curvature (mm) of the i-th surface from the object side, di (i=1, 2, 3, . . .) represents the i-th axial distance (mm) from the object side, and Ni (i=1, 2, 3, . . .) and vi (i=1, 2, 3, . . .) respectively represent the refractive index (Nd) for the d-line and the Abbe number (νd) of the i-th optical element from the object side. A surface whose radius of curvature ri is marked with an asterisk (*) is an aspherical surface, of which the surface shape is defined by formula (AS) noted earlier. Moreover, in the construction data, for each of those axial distances that vary with zooming (i.e. variable aerial distances), three values are given that are, from left, the axial distance at the wide-angle end W (the shortest-focal-length end), the axial distance in the middle position M (the middle-focal-length position), and the axial distance at the telephoto end T (the longest-focal-length end). Also listed are the focal length f, (in mm), the f-number FNO, and the view angle (2ω, °) of the entire optical system in those three focal-length positions W, M, and T, and the aspherical surface data. Table 10 lists the values of the conditional formulae as actually observed in Examples 1 to 9.

[0093] FIGS. 10A-10I, 11A-11I, 12A-12I, 13A-13I, 14A-14I, 15A-15I, 16A-16I, 17A-17I, and 18A-18I are aberration diagrams of Examples 1 to 9, respectively. Of these diagrams, FIGS. 10A-10C, 11A-11C, 12A-12C, 13A-13C, 14A-14C, 15A-15C, 16A-16C, 17A-17C, and 18A-18C show the aberration observed at the wide-angle end W, FIGS. 10D-10F, 11D-11F, 12D-12F, 13D-13F, 14D-14F, 15D-15F, 16D-16F, 17D-17F, and 18D-18F show the aberration observed in the middle position M, and FIGS. 10G-10I, 11G-11I, 12G-12I, 13G-13I, 14G-14I, 15G-15I, 16G-16I, 17G-17I, and 18G-18I show the aberration observed at the telephoto end T. Of these diagrams, FIG. 10A, 10D, 10G, 11A, 11D, 11G, 12A, 12D, 12G, 13A, 13D, 13G, 14A, 14D, 14G, 15A, 15D, 15G, 16A, 16D, 16G, 17A, 17D, 17G, 18A, 18D, and 18G show spherical aberration, FIG. 10B, 10E, 10H, 11B, 11E, 11H, 12B, 12E, 12H, 13B, 13E, 13H, 14B, 14E, 14H, 15B, 15E, 15H, 16B, 16E, 16H, 17B, 17E, 17H, 18B, 18E, and 18H show astigmatism, and FIG. 10C, 10F, 10I, 11C, 11F, 11I, 12C, 12F, 12I, 13C, 13F, 13I, 14C, 14F, 14I, 15C, 15F, 15I, 16C, 16F, 16I, 17C, 17F, 17I, 18C, 18F, and 18I show distortion. In these diagrams, Y′ represents the maximum image height (mm). In the diagrams showing spherical aberration, a solid line d, a dash-and-dot line g, and a dash-dot-dot line c show the spherical aberration for the d-line, for the g-line, and for the c-line, respectively, and a broken line SC shows the sine condition. In the diagrams showing astigmatism, a broken line DM and a solid line DS represent the astigmatism for the d-line on the meridional plane and on the sagittal plane, respectively. In the diagrams showing distortion, a solid line represents the distortion (%) for the d-line. TABLE 1 Construction Data of Example 1 f = 4.45 ˜ 7.8 ˜ 12.7, FNO = 2.84 ˜ 2.84 ˜ 2.90, 2ω = 75.8 ˜ 46.8 ˜ 28.9 Radius of Axial Refractive Abbe Curvature Distance Index Number r1 = 18.401 d1 = 0.800 N1 = 1.54072 ν1 = 47.22 r2 = 5.940 d2 = 3.275 ˜ 6.628 ˜ 5.000 r3* = −46.268 d3 = 0.800 N2 = 1.52200 ν2 = 52.20 r4* = 7.744 d4 = 1.115 r5 = 10.618 d5 = 1.784 N3 = 1.84666 ν3 = 23.82 r6 = 29.518 d6 = 14.440 ˜ 6.151 ˜ 2.201 r7 = ∞(ST) d7 = 0600 r8 = 10.096 d8 = 1.673 N4 = 1.75450 ν4 = 51.57 r9 = 35.493 d9 = 0.100 r10 = 6.646 d10 = 2.391 N5 = 1.75450 ν5 = 51.57 r11 = 42.505 d11 = 0.436 r12 = 372.791 d12 = 0.800 N6 = 1.84666 ν6 = 23.82 r13 = 5.188 d13 = 0.800 r14 = 6.476 d14 = 2.091 N7 = 1.52200 ν7 = 52.20 r15* = 43.112 d15 = 1.283 ˜ 8.292 ˜ 13.780 r16* = −50.000 d16 = 2.639 N8 = 1.75450 ν8 = 51.57 r17* = −9.674 d17 = 2.774 ˜ 0.700 ˜ 0.790 r18 = ∞ d18 = 2.000 N9 = 1.51680 ν9 = 64.20 r19 = ∞ Aspherical Surface Data of Surface r3 ε = 1.0000, A4 = 0.66858 × 10⁻³, A6 = −0.25227 × 10⁻⁴, A8 = 0.41627 × 10⁻⁶ Aspherical Surface Data of Surface r4 ε = 1.0000, A4 = 0.27983 × 10⁻³, A6 = −0.33808 × 10⁻⁴, A8 = 0.43681 × 10⁻⁶ Aspherical Surface Data of Surface r15 ε = 1.0000, A4 = 0.14395 × 10⁻², A6 = 0.21710 × 10⁻⁴, A8 = 0.13202 × 10⁻⁵ Aspherical Surface Data of Surface r16 ε = 1.0000, A4 = −0.39894 × 10⁻³, A6 = −0.41378 × 10^(−4,) A8 = 0.19806 × 10⁻⁵ Aspherical Surface Data of Surface r17 ε = 1.0000, A4 = 0.27510 × 10⁻³, A6 = −0.46341 × 10⁻⁴, A8 = 0.17216 × 10⁻⁵

[0094] TABLE 2 Construction Data of Example 2 f = 4.45 ˜ 7 8 ˜ 12.7, FNO = 2.67 ˜ 2.90 ˜ 2.90, 2ω = 76.9 ˜ 46.6 ˜ 28.5 Radius of Axial Refractive Abbe Curvature Distance Index Number r1 = 12.628 d1 = 1.000 N1 = 1.58913 ν1 = 61.25 r2 = 5.734 d2 = 3.800 ˜ 6.823 ˜ 4.759 r3* = −17.691 d3 = 0.800 N2 = 1.52200 ν2 = 52.20 r4* = 8.550 d4 = 1.669 r5 = 14.585 d5 = 1.500 N3 = 1.84666 ν3 = 23.78 r6 = 75.547 d6 = 12.939 ˜ 5.191 ˜ 1.490 r7 = ∞(ST) d7 = 0.600 r8 = 10.478 d8 = 1.730 N4 = 1.78831 ν4 = 47.32 r9 = 48.647 d9 = 0.100 r10 = 5.925 d10 = 2.491 N5 = 1.58913 ν5 = 61.25 r11 = 20.627 d11 = 0.010 N6 = 1.51400 ν6 = 42.83 r12 = 20.627 d1 = 0.700 N7 = 1.84666 ν7 = 23.78 r13 = 4.609 d13 = 0.632 r14 = 4.757 d14 = 2.626 N8 = 1.52200 ν8 = 52.20 r15* = 14.654 d15 = 1.439 ˜ 7.835 ˜ 13.100 r16* = −50.000 d16 = 1.000 N9 = 1.58340 ν9 = 30.23 r17* = 70.535 d17 = 0.591 r18 = −94.053 d18 = 1.802 N10 = 1.78590 ν10 = 43.93 r19 = −8.643 d19 = 2.371 ˜ 0.700 ˜ 1.200 r20 = ∞ d20 = 2.000 N11 = 1.51680 ν11 = 64.20 r21 = ∞ Aspherical Surface Data of Surface r3 ε = 1.0000, A4 = 0.56623 × 10⁻³, A6 = −0.23264 × 10⁻⁴, A8 = 0.30123 × 10⁻⁶ Aspherical Surface Data of Surface r4 ε = 1.0000, A4 = 0.43838 × 10⁻⁴, A6 = −0.28329 × 10⁻⁴, A8 = 0.33275 × 10⁻⁶ Aspherical Surface Data of Surface r15 ε = 10000, A4 = =0.21324 × 10⁻², A6 = 0.32366 × 10⁻⁴, A8 = 0.53566 × 10⁻⁵ Aspherical Surface Data of Surface r16 ε = 1.0000, A4 = 0.95453 × 10⁻³, A6 = −0.13928 × 10⁻³, A8 = 0.43729 × 10⁻⁵ Aspherical Surface Data of Surface r17 ε = 1.0000, A4 = 0.20120 × 10⁻², A6 = −0.13956 × 10⁻³, A8 = 0.38295 × 10⁻⁵

[0095] TABLE 3 Construction Data of Example 3 f = 4.45 ˜ 7.8 ˜ 12.7, FNO = 2.70 ˜ 2.84 ˜ 2.89, 2ω = 76.6 ˜ 46.4 ˜ 29.1 Radius of Axial Refractive Abbe Curvature Distance Index Number r1 = 11.274 d1 = 1.000 N1 = 1.74330 ν1 = 49.22 r2 = 5.143 d2 = 3.500 r3* = 302.871 d3 = 1.800 N2 = 1.52200 ν2 = 52.20 r4* = −39.780 d4 = 1.500 ˜ 3.907 ˜ 1.412 r5 = −20.000 d5 = 0.800 N3 = 1.63854 ν3 = 55.45 r6 = 10.669 d6 = 0.800 r7 = 12.450 d7 = 1.550 N4 = 1.84666 ν4 = 23.78 r8 = 48.662 d8 = 10.824 ˜ 3.774 ˜ 1.000 r9 = ∞(ST) d9 = 0.600 r10 = 11.059 d10 = 1.807 N5 = 1.77250 ν5 = 49.77 r11 = 137.002 d11 = 0.100 r12 = 7.339 d12 = 2.800 N6 = 1.75450 ν6 = 51.57 r13 = −37.431 d13 = 0.010 N7 = 1.51400 ν7 = 42.83 r14 = −37.431 d14 = 0.712 N8 = 1.84666 ν8 = 23.78 r15 = 6.744 d15 = 1.282 r16 = 9.773 d16 = 1.500 N9 = 1.52200 ν9 = 52.20 r17* = 33.228 d17 = 1.112 ˜ 7.313 ˜ 12.854 r18* = 22.508 d18 = 1.000 N10 = 1.58340 ν10 = 10.23 r19* = 8.706 d19 = 0.773 r20 = 53 706 d20 = 1.801 N11 = 1.78590 ν11 = 43.93 r21 = −10.576 d21 = 2.530 ˜ 0.971 ˜ 0.700 r22 = ∞ d2 = 2.000 N12 = 1.51680 ν12 = 64.20 r23 = ∞ Aspherical Surface Data of Surface r3 ε = 1.0000, A4 = 0.28635 × 10⁻³, A6 = 0.15667 × 10⁻⁴, A8 = −0.57168 × 10⁻⁶ Aspherical Surface Data of Surface r4 ε = 1.0000, A4 = −0.17053 × 10⁻³, A6 = 0.80129 × 10⁻⁵, A8 = −0.94476 × 10⁻⁶ Aspherical Surface Data of Surface r17 ε = 1.0000, A4 = 0.14359 × 10⁻², A6 = 0.19756 × 10⁻⁴, A8 = 0.24320 × 10⁻⁵ Aspherical Surface Data of Surface r18 ε = 1.0000, A4 = −0.14772 × 10⁻², A6 = −0 28230 × 10⁻⁴, A8 = 0.39925 × 10⁻⁵ Aspherical Surface Data of Surface r19 ε = 1.0000, A4 = −0.12532 × 10⁻², A6 = −0.15384 × 10⁻⁴, A8 = 0.28984 × 10⁻⁵

[0096] TABLE 4 Construction Data of Example 4 f = 4.45 ˜ 7.8 ˜ 12.7, FNO = 2.88 ˜ 2.81 ˜ 2.90, 2ω = 76.7 ˜ 46 ˜ 28.9 Radius of Axial Refractive Abbe Curvature Distance Index Number r1 = 12.938 d1 = 1.000 N1 = 1.74330 ν1 = 49.22 r2 = 5.796 d2 = 3.500 r3* = 44.528 d3 = 1.800 N2 = 1.52200 ν2 = 52.20 r4* = −104.899 d4 = 1.553 ˜ 3.953 ˜ 1.483 r5 = −20.000 d5 = 0.800 N3 = 1.63854 ν3 = 55.45 r6 = 10.131 d6 = 1.135 r7 = 13.404 d7 = 2.000 N4 = 1.84666 ν4 = 23.78 r8 = 61.168 d8 = 10.984 ˜ 3.778 ˜ 1.000 r9 = ∞(ST) d9 = 0.600 r10 = 11.382 d10 = 2.046 N5 = 1.77250 ν5 = 49.77 r11 = −52.132 d11 = 0.100 r12 = 7.001 d12 = 2.783 N6 = 1.75450 ν6 = 51.57 r13 = −24.543 d13 = 0.010 N7 = 1.51400 ν7 = 42 83 r14 = −24.543 d14 = 0.700 N8 = 1.84666 ν8 = 23.78 r15 = 6.105 d15 = 1.361 r16* = −22.829 d16 = 1.641 N9 = 1.52200 ν9 = 52.20 r17* = −17.058 d17 = 1.128 ˜ 7.052 ˜ 12.841 r18* = −50.000 d18 = 2.800 N10 = 1.74330 ν10 = 49.22 r19 = −10 303 d19 = 2.359 ˜ 1.241 ˜ 0.700 r20 = ∞ d20 = 2.000 N11 = 1.51680 ν11 = 64.20 r21 = ∞ Aspherical Surface Data of Surface r3 ε = 1.0000, A4 = 0.19527 × 10⁻³, A6 = 0.57342 × 10⁻⁸, A8 = −0.20853 × 10⁻⁶ Aspherical Surface Data of Surface r4 ε = 1.0000, A4 = −0.17096 × 10⁻³, A6 = −0.10072 × 10⁻⁴, A8 = −0.10753 × 10⁻⁶ Aspherical Surface Data of Surface r16 ε = 1.0000, A4 = −0.13142 × 10⁻², A6 = 0.94352 × 10⁻⁴, A8 = −0.12279 × 10⁻⁵ Aspherical Surface Data of Surface r17 ε = 1.0000, A4 = 0.11300 × 10⁻³, A6 = 0.11926 × 10⁻³, A8 = −0.60390 × 10⁻⁷ Aspherical Surface Data of Surface r18 ε = 1.0000, A4 = −0.50806 × 10⁻³, A6 = 0.29779 × 10⁻⁵, A8 = −0.38526 × 10⁻⁷

[0097] TABLE 5 Construction Data of Example 5 f = 4.8 ˜ 9.7 ˜ 15.5, FNO = 2.83 ˜ 2.85 ˜ 3.01, 2ω = 72.6 ˜ 36.8 ˜ 23.5 Radius of Axial Refractive Abbe Curvature Distance Index Number r1 = 11.104 d1 = 0.800 N1 = 1.74330 ν1 = 49.22 r2 = 6.378 d2 = 2.300 r3* = 14.802 d3 = 1.800 N2 = 1.52200 ν2 = 52.20 r4* = 20.396 d4 = 2.430 ˜ 5.010 ˜ 4.866 r5 = −20.000 d5 = 0.800 N3 = 1.63854 ν3 = 55.45 r6 = 9.907 d6 = 0.800 r7 = 10.952 d7 = 1.500 N4 = 1.84666 ν4 = 23.78 r8 = 27.854 d8 = 11.584 ˜ 3.183 ˜ 1.000 r9 = ∞(ST) d9 = 0.600 r10 = 16.003 d10 = 1.787 N5 = 1.77250 ν5 = 49.77 r11 = −34.803 d11 = 0.100 r12 = 6.218 d12 = 2.784 N6 = 1.75450 ν6 = 51.57 r13 = −93.239 d13 = 0.010 N7 = 1.51400 ν7 = 42.83 r14 = −93.241 d14 = 0.700 N8 = 1.84666 ν8 = 23.78 r15 = 5.710 d15 = 1.002 r16 = 11.201 d16 = 1.500 N9 = 1.52200 ν9 = 52.20 r17* = 16.808 d17 = 1.180 ˜ 7.784 ˜ 13.237 r18* = −50.000 d18 = 1.000 N10 = 1.58340 ν10 = 30.23 r19* = −55.066 d19 = 0.515 r20 = 37.772 d20 = 1.500 N11 = 1.78590 ν11 = 43.93 r21 = −20.359 d21 = 1.609 ˜ 0.825 ˜ 0.700 r22 = ∞ d22 = 2.000 N12 = 1.51680 ν12 = 64.20 r23 = ∞ Aspherical Surface Data of Surface r3 ε = 1.0000, A4 = −0.68378 × 10⁻⁴, A6 = 0.91459 × 10⁻⁵, A8 = −0.17059 × 10⁻⁶ Aspherical Surface Data of Surface r4 ε = 1.0000, A4 = −0.30623 × 10⁻³, A6 = 0.77956 × 10⁻⁵, A8 = −0.26508 × 10⁻⁶ Aspherical Surface Data of Surface r17 ε = 1.0000, A4 = 0.15313 × 10⁻², A6 = 0.48360 × 10⁻⁴, A8 = 0.33469 × 10⁻⁵ Aspherical Surface Data of Surface r18 ε = 1.0000, A4 = 0.33814 × 10⁻², A6 = −0.12472 × 10⁻³, A8 = 0.45839 × 10⁻⁵ Aspherical Surface Data of Surface r19 ε = 1.0000, A4 = 0.39759 × 10⁻², A6 = −0.12370 × 10⁻³, A8 = 0.47201 × 10⁻⁵

[0098] TABLE 6 Construction Data of Example 6 f = 3.0 ˜ 5.2 ˜ 8.6, FNO = 2.30 ˜ 3.18 ˜ 4.10, 2ω = 76.7 ˜ 46.2 ˜ 28.2 Radius of Axial Refractive Abbe Curvature Distance Index Number r1 = 18.376 d1 = 0.750 N1 = 1.75450 ν1 = 51.57 r2 = 5.908 d2 = 2.654 ˜ 5.660 ˜ 2.654 r3* = −38.428 d3 = 0.750 N2 = 1.52510 ν2 = 56.38 r4* = 3.454 d4 = 1.298 r5 = 6.786 d5 = 2.177 N3 = 1.58340 ν3 = 30.23 r6 = −250.470 d6 = 9.631 ˜ 2.374 ˜ 1.000 r7 = ∞(ST) d7 = 0.600 r8 = 4.468 d8 = 4.230 N4 = 1.76822 ν4 = 46.58 r9 = −5.283 d9 = 0.010 N5 = 1.51400 ν5 = 42.83 r10 = −5.283 d10 = 0.750 N6 = 1.84666 ν6 = 23.82 r11* = 12.622 d11 = 2.573 ˜ 6.824 ˜ 11.205 r12 = −17.607 d12 = 1.478 N7 = 1.52510 ν7 = 56.38 r13* = −5.316 d13 = 0.500 r14 = ∞ d14 = 3.400 N8 = 1.51680 ν8 = 64.20 r15 = ∞ Aspherical Surface Data of Surface r3 ε = 1.0000, A4 = −0.22743 × 10⁻³, A6 = 0.81018 × 10⁻⁴, A8 = −0.11992 × 10⁻⁴ Aspherical Surface Data of Surface r4 ε = 1.0000, A4 = −0.34914 × 10⁻², A6 = −0.12871 × 10⁻³, A8 = −0.99555 × 10⁻⁵ Aspherical Surface Data of Surface r11 ε = 1.0000, A4 = 0.47689 × 10⁻², A6 = 0.18896 × 10⁻³, A8 = 0.77520 × 10⁻⁴ Aspherical Surface Data of Surface r13 ε = 1.0000, A4 = 0.26471 × 10⁻², A6 = −0.51516 × 10⁻⁴, A8 = 0.18942 × 10⁻⁵

[0099] TABLE 7 Construction Data of Example 7 f = 2.5 ˜ 4.8 ˜ 7.3, FNO = 2.37 ˜ 3.33 ˜ 4.10, 2ω = 72.9 ˜ 40.4 ˜ 26.7 Radius of Axial Refractive Abbe Curvature Distance Index Number r1 = 16.241 d1 = 0.800 N1 = 1.75450 ν1 = 51.57 r2 = 5.499 d2 = 3.085 ˜ 5.394 ˜ 3.085 r3* = 23.072 d3 = 1.000 N2 = 1.52510 ν2 = 56.38 r4* = 3.156 d4 = 1.390 r5 = 5.079 d5 = 1.653 N3 = 1.84666 ν3 = 23.82 r6 = 7.886 d6 = 9.655 ˜ 3.023 ˜ 1.879 r7 = ∞(ST) d7 = 0.600 r8 = 4.268 d8 = 3.824 N4 = 1.73299 ν4 = 52.32 r9 = −5.710 d9 = 0.010 N5 = 1.51400 ν5 = 42.83 r10 = −5.710 d10 = 0.750 N6 = 1.84666 ν6 = 23.82 r11* = 27.698 d11 = 1.576 ˜ 5.899 ˜ 9.351 r12 = −12.089 d12 = 2.546 N7 = 1.52510 ν7 = 56.38 r13* = −4.510 d13 = 0.500 r14 = ∞ d14 = 3.400 N8 = 1.51680 ν8 = 64.20 r15 = ∞ Aspherical Surface Data of Surface r3 ε = 1.0000, A4 0.11334 × 10⁻², A6 = 0.83390 × 10⁻⁴, A8 = −0 24186 × 10⁻⁴ Aspherical Surface Data of Surface r4 ε 1.0000, A4 = −0.14398 × 10⁻², A6 = −0.68030 × 10⁻⁴, A8 = −0.49071 × 10⁻⁴ Aspherical Surface Data of Surface r11 ε = 1.0000, A4 = 0.43753 × 10⁻², A6 = 0.23651 × 10⁻³, A8 = 0.47406 × 10⁻⁴ Aspherical Surface Data of Surface r13 ε = 1.0000, A4 = 0.35646 × 10⁻², A6 = −0.42883 × 10^(−4,) A8 = 0.14875 × 10⁻⁵

[0100] TABLE 8 Construction Data of Example 8 f = 1.6 ˜ 3.0 ˜ 4.6, FNO = 2.44 ˜ 3.37 ˜ 4.10, 2ω = 76.4 ˜ 43.8 ˜ 28.8 Radius of Axial Refractive Abbe Curvature Distance Index Number r1 = 7.967 d1 = 0.800 N1 = 1.75450 ν1 = 51.57 r2 = 3.205 d2 = 2.923 ˜ 4.841 ˜ 3.019 r3* = 14.015 d3 = 1.000 N2 = 1.52510 ν2 = 56.38 r4* = 2.338 d4 = 2.084 r5 = 5.334 d5 = 3.470 N3 = 1.84666 ν3 = 23.82 r6 = 8.028 d6 = 7.717 ˜ 2.047 ˜ 1.000 r7 = ∞(ST) d7 = 0.600 r8 = 4.296 d8 = 3.644 N4 = 1.76050 ν4 = 50.55 r9 = −4.200 d9 = 0.010 N5 = 1.51400 ν5 = 42.83 r10 = −4.200 d10 = 0.750 N6 = 1.84666 ν6 = 23.82 r11* = −159.225 d11 = 0.897 ˜ 4.648 ˜ 7.518 r12 = −8.166 d12 = 2.207 N7 = 1.52510 ν7 = 56.38 r13* = −3.963 d13 = 0.500 r14 = ∞ d14 = 3.400 N8 = 1.51680 ν8 = 64.20 r15 = ∞ Aspherical Surface Data of Surface r3 ε = 1.0000, A4 = 0.19149 × 10⁻², A6 = 0.14015 × 10⁻², A8 = −0.37347 × 10⁻³, A10 = 0.31010 × 10⁻⁴ Aspherical Surface Data of Surface r4 ε = 1.0000, A4 = −0.67645 × 10⁻², A6 = −0.60143 × 10⁻⁴, A8 = −0.46412 × 10⁻³ Aspherical Surface Data of Surface r11 ε = 1.0000, A4 = 0.37565 × 10⁻², A6 = 0.66871 × 10⁻³, A8 = −0.80434 × 10⁻⁴ Aspherical Surface Data of Surface r13 ε = 1.0000, A4 = 0.52954 × 10⁻², A6 = −0.75580 × 10⁻³, A8 = 0.15734 × 10⁻³

[0101] TABLE 9 Construction Data of Example 9 f = 4.5 ˜ 7.8 ˜ 12.7, FNO = 3.24 ˜ 3.09 ˜ 4.13, 2ω = 76.4 ˜ 47.9 ˜ 29.6 Radius of Axial Refractive Abbe Curvature Distance Index Number r1 = 21.240 d1 = 1.200 N1 = 1.75450 ν1 = 51.57 r2 = 5.872 d2 = 3.000 ˜ 8.500 ˜ 4.979 r3* = 8.946 d3 = 1.000 N2 = 1.62112 ν2 = 57.62 r4* = 4.431 d4 = 2.156 r5 = 7.067 d5 = 2.000 N3 = 1.84666 ν3 = 23.82 r6 = 9.677 d6 = 11.453 ˜ 2.003 ˜ 1.000 r7 = ∞(ST) d7 = 0.600 r8* = 5.559 d8 = 1.675 N4 = 1.57965 ν4 = 60.49 r9 = 13.046 d9 = 0.100 r10 = 6.192 d10 = 2.500 N5 = 1.48749 ν5 = 70.44 r11 = −11.918 d11 = 0.203 r12 = −14.208 d12 = 3.421 N6 = 1.79850 ν6 = 22.60 r13* = 21.481 d13 = 0.780 r14 = 14.579 d14 = 4.000 N7 = 1.75450 ν7 = 51.57 r15* = 12.388 d15 = 1.898 ˜ 5.848 ˜ 10.372 r16 = ∞ d16 = 2.000 N8 = 1.51680 ν8 = 64.20 r17 = ∞ Aspherical Surface Data of Surface r3 ε = 1.0000, A4 = 0.13577 × 10⁻², A6 = −0.10949 × 10⁻³, A8 = 0.37797 × 10⁻⁵ Aspherical Surface Data of Surface r4 ε = 1.0000, A4 = 0.65141 × 10⁻³, A6 = −0.18413 × 10⁻³, A8 = 0.34984 × 10⁻⁵ Aspherical Surface Data of Surface r8 ε = 1.0000, A4 = −0.30607 × 10⁻³, A6 = −0.12679 × 10⁻⁴, A8 = −0.66500 × 10⁻⁶ Aspherical Surface Data of Surface r13 ε = 1.0000, A4 = 0.28699 × 10⁻², A6 = 0.29442 × 10⁻⁵, A8 = 0.14242 × 10⁻⁴ Aspherical Surface Data of Surface r15 ε = 1.0000, A4 = −0.73341 × 10⁻³, A6 = 0.14643 × 10⁻³, A8 = −0.36100 × 10⁻⁵

[0102] TABLE 10 Actual Values of Conditional Formulae (3) (4) (5) Y = 0.7 Ymax (6) (1) (2) (tanωw)² · TLw□Fnt/ (|X| − |X0|) (CR1 − CR2)/ (7) Ex. f1/f2 |f12/fw| fw/TLw (fw · tanωw) [C0(N′ − N)f3] (CR1 + CR2) |f12/f3| 1 2.620 2.482 0.065 34.43 −0.267 0.676 1.024 2 1.434 2.416 0.068 33.65 −0.094 — 1.042 3 1.426 2.140 0.068 33.71 −0.499 — 0.974 4 1.131 2.270 0.067 34.19 −0.023 0.658 1.017 5 0.773 2.315 0.066 33.59 −0.091 — 1.203 6 1.443 2.268 0.059 55.29 −0.033 0.054 0.873 7 1.337 2.260 0.043 69.95 −0.090 0.457 0.817 8 1.269 2.206 0.032 101.59 −0.069 0.347 0.590 9 3.909 1.812 0.071 46.08 0.002 — 1.023 

What is claimed is:
 1. An optical device comprising: a zoom lens system, comprising a plurality of lens units, which achieves zooming by varying unit-to-unit distances; and an image sensor for converting an optical image formed by the zoom lens system into an electrical signal, wherein the zoom lens system comprises at least, from an object side thereof to an image side thereof, a first lens unit having a negative optical power, a second lens unit having a negative optical power, and a third lens unit having a positive optical power.
 2. An optical device as claimed in claim 1 wherein the zoom lens system further comprises a low pass filter which adjusts spatial frequency characteristics of the optical image formed by the zoom lens system, said low-pass filter located between the first lens unit and the image sensor.
 3. An optical device as claimed in claim 2 wherein the first lens unit and the low-pass filter remain stationary during zooming.
 4. An optical device as claimed in claim 1 wherein the first lens unit is a single lens element.
 5. An optical device as claimed in claim 1 wherein the first lens unit comprises two lens elements.
 6. An optical device as claimed in claim 1 wherein the third lens unit comprises at least two positive lens elements and at least one negative lens element.
 7. An optical device as claimed in claim 1 wherein the third lens unit has an aspherical surface at the image side thereof.
 8. An optical device as claimed in claim 7 wherein the following conditional formulae are fulfilled: −0.6<(|X|−|X0|)/[C0·(N′−N)·f3]<0 0.1Ymax≦Y≦0.7Ymax wherein X represents a surface shape of the aspherical surface; X0 represents a surface shape of a reference spherical surface of the aspherical surface; C0 represents a curvature of the reference spherical surface of the aspherical surface; N represents a refractive index for a d-line of the object-side medium of the aspherical surface; N′ represents the refractive index for the d-line of the image-side medium of the aspherical surface; f3 represents a focal length of the third lens unit; Ymax represents a maximum effective optical path of an aspherical surface; and Y represents a height in a direction perpendicular to an optical axis.
 9. An optical device as claimed in claim 1 wherein the following conditional formula is fulfilled: 0.5<f1/f2<5 wherein f1 represents a focal length of the first lens unit; and f2 represents a focal length of the second lens unit.
 10. An optical device as claimed in claim 1 wherein the following conditional formulae are fulfilled: 1.5<|f12/fw|<4 0.058<(tan ωw)²×fw/TLw<0.9 wherein f12 represents a composite focal length of the first and the second lens units at a wide-angle end; fw represents a focal length of an entire optical system at the wide-angle end; tan ωw represents a half view angle at a wide-angle end; fw represents a focal length of an entire optical system at the wide-angle end; and TLw represents a distance from a first vertex to an image plane at the wide-angle end.
 11. An optical device as claimed in claim 1 wherein the following conditional formula is fulfilled: 1.5<|f12/fw|<4 10<TLw×Fnt/(fw×tan ωw)<50 where TLw represents a distance from a first vertex to an image plane at a wide-angle end; Fnt represents an f-number at a telephoto end; f12 represents a composite focal length of the first and the second lens units at the wide-angle end; fw represents a focal length of an entire optical system at the wide-angle end; and tan ωw represents a half view angle at the wide-angle end.
 12. An optical device as claimed in claim 1 wherein the lens unit closest to the image side has a positive optical power, said lens unit is comprised of at least one positive lens element and the positive lens element fulfills the following conditional formula: 0.05<(CR1−CR2)/(CR1+CR2)<5 wherein CR1 represents a radius of curvature of the object-side surface; and CR2 represents a radius of curvature of the image-side surface.
 13. An optical device as claimed in claim 1 wherein the following conditional formula is fulfilled: 0.4<|f12/f3|<1.5 where f12 represents a composite focal length of the first and the second lens units at a wide-angle end; and f3 represents a focal length of the third lens unit.
 14. An optical device comprising: a zoom lens system, comprising a plurality of lens units, which achieves zooming by varying unit-to-unit distances; and an image sensor for converting an optical image formed by the zoom lens system into an electrical signal, wherein the zoom lens system comprises at least, from an object side thereof to an image side thereof, a first lens unit having a negative optical power, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a fourth lens unit having a positive optical power.
 15. An optical device as claimed in claim 14 wherein the zoom lens system achieves zooming by varying distances between the first lens unit to the fourth lens unit.
 16. An optical device as claimed in claim 15 wherein the zoom lens system further comprises a low-pass filter which adjusts spatial frequency characteristics of the optical image formed by the zoom lens system, said low-pass filter located between the first lens unit and the image sensor.
 17. An optical device as claimed in claim 16 wherein the first lens unit and the low-pass filter remain stationary during zooming.
 18. An optical device as claimed in claim 14 wherein the first lens unit is a single lens element.
 19. An optical device as claimed in claim 14 wherein the first lens unit comprises two lens elements.
 20. An optical device as claimed in claim 14 wherein the third lens unit comprises at least two positive lens elements and at least one negative lens element.
 21. An optical device as claimed in claim 14 wherein the third lens unit has an aspherical surface at the image side thereof.
 22. An optical device as claimed in claim 21 wherein the following conditional formula is fulfilled: −0.6<(|X|−|X0|)/[C0·(N′−N)·f3]<0 0.1Ymax≦Y≦0.7Ymax wherein X represents a surface shape of the aspherical surface; X0 represents a surface shape of a reference spherical surface of the aspherical surface; C0 represents a curvature of the reference spherical surface of the aspherical surface; N represents a refractive index for a d-line of the object-side medium of the aspherical surface; N′ represents the refractive index for the d-line of the image-side medium of the aspherical surface; f3 represents a focal length of the third lens unit; Ymax represents a maximum effective optical path of an aspherical surface; and Y represents a height in a direction perpendicular to an optical axis.
 23. An optical device as claimed in claim 14 wherein the following conditional formula is fulfilled: 0.5<f1/f2<5 wherein f1 represents a focal length of the first lens unit; and f2 represents a focal length of the second lens unit.
 24. An optical device as claimed in claim 14 wherein the following conditional formulae are fulfilled: 1.5<|f12/fw|<4 0.058<(tan ωw)²×fw/TLw<0.9 wherein f12 represents a composite focal length of the first and the second lens units at a wide-angle end; fw represents a focal length of an entire optical system at the wide-angle end; tan ωw represents a half view angle at a wide-angle end; fw represents a focal length of an entire optical system at the wide-angle end; and TLw represents a distance from a first vertex to an image plane at the wide-angle end.
 25. An optical device as claimed in claim 14 wherein the following conditional formula is fulfilled: 1.5<|f12/fw|<4 10<TLw×Fnt/(fw×tan ωw)<50 where TLw represents a distance from a first vertex to an image plane at a wide-angle end; Fnt represents an f-number at a telephoto end; f12 represents a composite focal length of the first and the second lens units at the wide-angle end; fw represents a focal length of an entire optical system at the wide-angle end; and tan ωw represents a half view angle at the wide-angle end.
 26. An optical device as claimed in claim 14 wherein the lens unit closest to the image side has a positive optical power, said lens unit is comprised of at least one positive lens element and the positive lens element fulfills the following conditional formula: 0.05<(CR1−CR2)/(CR1+CR2)<5 wherein CR1 represents a radius of curvature of the object-side surface; and CR2 represents a radius of curvature of the image-side surface.
 27. An optical device as claimed in claim 14 wherein the following conditional formula is fulfilled: 0.4<|f12/f3<1.5 where f12 represents a composite focal length of the first and the second lens units at a wide-angle end; and f3 represents a focal length of the third lens unit.
 28. A digital camera comprising: an optical lens device, and a memory; wherein said optical lens device comprises a zoom lens system, and an image sensor; wherein said zoom lens system includes a plurality of lens units which achieve zooming by varying unit-to-unit distances; and said image sensor converts an optical image formed by said zoom lens system into an electrical signal; wherein the zoom lens system comprises at least, from an object side thereof to an image side thereof, a first lens unit having a negative optical power, a second lens unit having a negative optical power, and a third lens unit having a positive optical power; and wherein said memory is adapted for storing image data from said image sensor, and said memory is not removable from said digital camera.
 29. A digital camera as claimed in claim 28 wherein the optical device further comprises a low-pass filter which adjusts spatial frequency characteristics of the optical image formed by the zoom lens system, said low-pass filter located between the first lens unit and the image sensor.
 30. A digital camera comprising: an optical lens device; and a memory; wherein said optical lens device comprises a zoom lens system, and an image sensor; wherein said zoom lens system includes a plurality of lens units which achieve zooming by varying unit-to-unit distances; and said image sensor converts an optical image formed by said zoom lens system into an electrical signal; wherein the zoom lens system comprises at least, from an object side thereof to an image side thereof, a first lens unit having a negative optical power, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a forth lens unit having a positive optical power; and wherein said memory is adapted for storing image data from said image sensor, and said memory is not removable from said digital camera.
 31. A digital camera as claimed in claim 30 wherein the optical device further comprises a low-pass filter which adjusts spatial frequency characteristics of the optical image formed by the zoom lens system, said low-pass filter located between the first lens unit and the image sensor. 